a. \(\dfrac{-13}{15}+\dfrac{5}{-18}\\ =\dfrac{-13}{15}+-\dfrac{5}{18}\\ =\dfrac{-234}{270}+-\dfrac{75}{270}=\dfrac{-309}{270}=\dfrac{-103}{90}\)
b. \(-\dfrac{2}{5}--\dfrac{3}{11}\\ =-\dfrac{22}{55}--\dfrac{15}{55}\\ =-\dfrac{7}{55}\)
b / \(=-\dfrac{13}{15}-\dfrac{5}{18}=-\dfrac{78}{90}-\dfrac{25}{90}=\dfrac{-103}{90}\)
c/ \(=-\dfrac{2}{5}+\dfrac{3}{11}=-\dfrac{22}{55}+\dfrac{15}{55}=\dfrac{7}{55}\)
`-13/15 + 5/-18`
` = -13/15 + (-5/18)`
` = -78/90 + (-25/90)`
\(=\dfrac{-78+\left(-25\right)}{90}\)
\(=-\dfrac{108}{90}\)
\(-\dfrac{2}{5}-\left(-\dfrac{3}{11}\right)\)
\(=-\dfrac{2}{5}+\dfrac{3}{11}\)
\(=-\dfrac{22}{55}+\dfrac{15}{55}\)
\(=-\dfrac{7}{55}\)
